Single-pole multi-throw switch having low parasitic reactance, and an antenna incorporating the same

ABSTRACT

A switch arrangement comprises a plurality of MEMS switches arranged on a substrate about a central point, each MEMS switch being disposed on a common imaginary circle centered on the central point. Additionally, and each MEMS switch is preferably spaced equidistantly along the circumference of the imaginary circle. Connections are provided for connecting a RF port of each one of the MEMS switches with the central point.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional PatentApplication No. 60/381,099 filed on May 15, 2002, which application isincorporated herein by reference.

TECHNICAL FIELD

[0002] This invention relates to single-pole, multi-throw switches thatare built using single-pole, single-throw devices combined in a hybridcircuit. The switches of this invention are symmetrically located arounda central point which is a vertical via in a multi layer printed circuitboard. BACKGROUND OF THE INVENTION AND CROSS REFERENCE TO RELATEDAPPLICATIONS

[0003] This application incorporates by reference the disclosure of U.S.Provisional Patent Application Serial No. ______ filed ______ andentitled “RF MEMS Switch with Integrated Impedance Matching Structure”(attorney docket 620650-7).

[0004] In one aspect, this invention addresses several problems withexisting single-pole, multi-throw switches built using single-pole,single-throw devices preferably combined in a switch matrix. Accordingto this aspect of the invention, the switches are symmetrically locatedaround a central point which is preferably a vertical via in a multilayer printed circuit board. In this way, a maximum number of switchescan be located around the common port with a minimum amount ofseparation. This leads to the lowest possible parasitic reactance, andgives the circuit the greatest possible frequency response. Furthermore,any residual parasitic reactance can be matched by a single element onthe common port, so that all ports will have the same frequencyresponse. This patent describes a 1×4 switch, but the concept may beextended to a 1×6 switch or to a 1×8 switch or a switch with evengreater fan out (1×N). Also, such a switch can be integrated with anantenna array for the purpose of producing a switched beam diversityantenna.

[0005] The switch arrangement disclosed herein can be conveniently usedwith a Vivaldi Cloverleaf Antenna to determine which antenna of theVivaldi Cloverleaf Antenna is active. U.S. patent application Ser. No.09/525,832 entitled “Vivaldi Cloverleaf Antenna” filed Mar. 12, 2000,the disclosure of which is hereby incorporated herein by this reference,teaches how Vivaldi Cloverleaf Antennas may be made.

[0006] The present invention has a number of possible applications anduses. As a basic building block in any communication system, and inmicrowave systems in general, a single-pole, multi-throw radio frequencyswitch has numerous applications. As communication systems getincreasingly complicated, and they require diversity antennas,reconfigurable receivers, and space time processing, the need for moresophisticated radio frequency components will grow. These advancedcommunications systems will need single-pole multi-throw switches havinglow parasitic reactance. Such switches will be used, for example, inconnection with the antenna systems of these communication systems.

[0007] The prior art includes the following:

[0008] (1) M. Ando, “Polyhedral Shaped Redundant Coaxial Switch”, U.S.Pat. No. 6,252,473 issued Jun. 26, 2001 and assigned to HughesElectronics Corporation. This patent describes a waveguide switch usingbulk mechanical actuators.

[0009] (2) B. Mayer, “Microwave Switch with Grooves for Isolation of thePassages”, U.S. Pat. No. 6,218,912 issued Apr. 17, 2001 and assigned toRobert Bosch GmbH. This patent describes a waveguide switch with amechanical rotor structure.

[0010] Neither of the patents noted above address issues that areparticular to the needs of a single-pole multi-throw switch of the typedisclosed herein. Although they are of a radial design, they are builtusing a conventional waveguide rather than (i) MEM devices and (ii)microstrips. It is not obvious that a radial design could be used for aMEM device switch and/or a microstrip switch because the necessaryvertical through-ground vias are not commonly used in microstripcircuits. Furthermore, the numerous examples of microstrip switchesavailable in the commercial marketplace do not directly apply to thisinvention because they typically use PIN diodes or FET switches, whichcarry certain requirements for the biasing circuit that dictate thegeometry and which are not convenient for use in a radial design.

[0011] There is a need for single-pole, multi-throw switches as ageneral building block for radio frequency communication systems. Onemeans of providing such devices that have the performance required formodern Radio Frequency (RF) systems is to use RF MicroElectro-Mechanical System (MEMS) switches. One solution to this problemwould be to simply build a 1×N monolithic MEMS switch on a singlesubstrate. However, there may be situations in which this is notpossible, or when one cannot achieve the required characteristics in amonolithic solution, such as a large fan-out number for example. Inthese situations, a hybrid approach should be used.

[0012] There are numerous ways to assemble single-pole, single-throw RFMEMS switches on a microwave substrate, along with RF lines to createthe desired switching circuit. Possibly the most convenient way is shownin FIG. 1. A common port, represented here as a microstrip line 5, endsat a point 6 near which several RF MEMS switches 10-1 through 10-4 areclustered. RF MEMS switches 10-1 through 10-4 are preferably spacedequidistantly from a centerline of microstrip 5 and laterally on eachside of it. Ports 1, 2, 3, and 4 then spread out from this central point6, with each port being addressed by a single MEMS switch 10. Thesubstrate, of which only a portion is shown, is represented by element12. By closing one of the switches (for example, switch 10-4), andopening all of the others (for example, switches 10-1 through 10-3), RFenergy can be directed from the common port provided by microstrip line5 to the chosen selectable port (port 4 in this example) with very lowloss. This switching circuit will also demonstrate high isolationbetween the common port and the three open ports, as well as highisolation between each of the selectable ports.

[0013] While the design depicted by FIG. 1 is believed to be novel, ithas several flaws. Ideally, all four MEMS devices 10-1 through 10-4should be clustered as close as reasonably possible around a singlepoint 6. In FIG. 1, note that switches 10 have different spacings fromend point 6. When the switches 10 are separated by a length oftransmission line, as is the case in FIG. 1, that length of transmissionline will then serve as a parasitic reactance to some of the ports. Forexample, in FIG. 1, the length or portion of transmission linedesignated by the letter “L” appears as an open microstrip stub to ports1 and 2. This length L of microstrip 6 is referred to as a “stub” in theantenna art and it affects the impedance of the circuit in which itappears. The effect, in this embodiment, is likely to be undesirable.Unfortunately, the second pair of ports 3, 4 likely may not be broughtany closer to the first pair 1, 2, because this would cause unwantedcoupling between the closely spaced sections of microstrip line thatwould result. Furthermore, if one wanted to compensate for the parasiticreactance caused by the microstrip stub, one would need to separatelytune each of the lines because they do not all see the same reactance.There may not be space on the top side of the circuit to allow aseparate tuning element for each of the selectable ports, and stillallow room for the DC bias lines and the RF signal lines.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

[0014]FIG. 1 depicts a rather straightforward way of combiningsingle-pole, single-throw RF MEMS switches into a single-pole,multi-throw hybrid design; however, the preferred designs are describedwith reference to the remaining figures.

[0015] In one aspect, the invention provides a switch arrangementcomprising a plurality of MEMS switches arranged on a substrate about acentral point, each MEMS switch being disposed on a common imaginarycircle centered on said central point, and each MEMS switch being spacedequidistantly along the circumference of said imaginary circle; andconnections for connecting a RF port of each one of said MEMS switcheswith said central point.

[0016] In another aspect, the invention provides a method of making aswitch arrangement comprising: disposing a plurality of MEMS switches ona substrate in a circular pattern about a point; disposing a pluralityof RF lines disposed in a radial pattern relative to said point on saidsubstrate; and connecting said plurality of RF strip lines to a commonjunction point at said point on said substrate via said plurality ofMEMS switches whereby operation of a one of said plurality of MEMSswitches couples a one of said plurality of RF strip lines to saidcommon junction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 depicts one technique for combining single-pole,single-throw RF MEMS switches into a single-pole, multi-throw hybriddesign;

[0018]FIGS. 2a and 2 b are top and side elevation views of oneembodiment of the present invention;

[0019]FIGS. 3a and 3 b are top and side elevation views of anotherembodiment of the present invention;

[0020]FIG. 4 shows a modification to the embodiment of FIGS. 3a and 3 b;

[0021]FIGS. 5a and 5 b are top and side elevation views of yet anotherembodiment of the present invention;

[0022]FIGS. 6a and 6 b are top and side elevation views of still anotherembodiment of the present invention;

[0023]FIG. 7 depicts a switching arrangement of FIGS. 5a and 5 b used incombination with a flared notch antenna;

[0024]FIG. 8 depicts a switching arrangement of FIGS. 5a and 5 b used incombination with a flared notch antenna having eight flared notchelements; and

[0025]FIG. 9 depicts another improvement compared to the switch of FIG.1.

DETAILED DESCRIPTION

[0026] Recall FIG. 1 and the fact that this design poses a number ofproblems in terms of the impedances seen from the common port of themicrostrip line 6 when the various ports 1-4 are switched on. Onesolution to this problem is shown in FIGS. 2a and 2 b. The structure ofFIGS. 2a and 2 b preferably consists of a multi-layer printed circuitboard 12, on which a common RF line 14 is formed on the bottom side 13of the board 12, and is fed through a ground plane 18 by a metal platedvia 20 to a central point 7 in the center of a 1×4 switch matrix ofswitches 10-1 through 10-4, which switches may be made as a hybrid on acommon substrate (not shown) or which may be individually attached tosurface 9. Switches 10-1 through 10-4 comprise a set of RF MEMS switches10 (the numeral 10 when used without a dash and another numeral is usedherein to refer to these RF MEMS switches in general as opposed to aparticular switch). As will be seen, the number of switches 10 in theset can be greater than four, if desired.

[0027] RF MEMS switches 10 are positioned around common point 7,preferably in a radial geometry as shown. The benefit of this geometryis that each of the selectable ports 1-4 sees the same RF environment(including the same impedance) by utilizing the same local geometrywhich is preferably only varied by rotation about an axis “A” definedthrough common point 7. Therefore, each of the ports 1-4 should have thesame RF performance (or, at least, nearly identical RF performances toeach other). Furthermore, since this geometry permits the MEMS devices10 to be clustered as closely as possible around common point 7,parasitic reactance should be minimized. Moreover, for the case of a 1×4switch matrix, control line pairs 11 can be arranged at right angles toeach other, resulting in very low coupling between them. This embodimenthas four ports, but, as will be seen, this basic design can be modifiedto provide a greater (or lesser) number of ports.

[0028] The MEMS switches 10 are preferably disposed in a circulararrangement around central point 7 on substrate 12. Note that theswitches 10 lie on a circular arrangement as indicated by the circularline identified by the letter B. Note also that the switches arepreferably arranged equidistantly along the circumference of thecircular line identified by the letter B. The MEMS switches 10 can beplaced individually directly on surface 9 of the circuit board 12 orthey may be formed on a small substrate (not shown) as a switch hybrid,which is in turn mounted on surface 9.

[0029] Via 20 preferably has a pad 8 on the top surface of the printedcircuit board 12 to which the MEMS switches 10 can be wired, forexample, using ball bonding techniques. The switches 10 are also wiredto the control lines pairs 11 and to the ports 1-4.

[0030] In FIG. 2a common port 7 is fed from the underside of the groundplane through a vertical metal plated via 20 to the top side of theboard 12 where it terminates at central point 7. MEMS switches 10 areradially clustered around this central point. The centers of the MEMSswitches 10 are preferably spaced a common distance (a common radius)away from an axis A of the via 20. This allows a large number ofswitches 10 to be fit into a small area, yet allows the coupling betweenthe ports to be minimized. In the particular case of the 1×4 switch,with MEMS switches 10-1-10-4, the coupling is further minimized by thefact that the RF microstrip lines directed to ports 1-4 are disposed atright angles to each other. The substrate 12 of this structurepreferably is a multi-layer microwave substrate with a buried groundplane 18.

[0031] The RF microstrip lines coupling to ports 1-4 may form the drivenelements of an antenna structure, for example, or may be coupled toantenna elements. Such elements may be used for sending and/or receivingRF signals.

[0032]FIGS. 3a and 3 b show another embodiment of the present invention,in which some of the DC bias lines are implemented as vias 21 whichconnect with the buried ground plane 18 in substrate 12. The vias 21 mayhave pads 8 formed on their top surfaces in order to facilitateconnecting the ground connections on the MEMS switches 10 thereto. Sinceeach bias line pair 11 consists of a ground line 24 and a signal orcontrol line 23, each of the ground lines 24-1-24-4, may be tied to theRF ground plane 18, with no loss of performance, by means of vias 21.This results in fewer external connections to the circuit because onlyone DC control connection 23-1-23-4 is needed for each switch 10-1-10-4,which is half as many total connections compared with the embodiment ofFIGS. 2a and 2 b.

[0033] An additional possible advantage of the geometry of FIGS. 3a and3 c is shown in FIG. 4. A feed-through via 20 such as that used for thecommon port 7 can sometimes have its own parasitic reactance. Byproviding a complementary reactance Z as an external lumped element 25,one may optimize the RF match of the circuit. In FIG. 4 the reactance Zcouples via 20 to ground using one of the vias 21 coupled to groundplane 18. Since the impedance match is done on the central port 7, andall other ports are symmetrical, the same matching structure Z will workfor all of the ports. This lumped element solution is one example of amatching structure, and others will be apparent to those skilled in theart of RF design. The ground connections of the MEMS switches 10 arewired to metal plated vias 21 directly or to their associated pads 8,either of which is in electrical communication with the buried groundplane 18. Note that the via 20 that provides the central RF port passesthrough a hole or opening 19 in the ground plane 18, while the vias 21contact the ground plane 18.

[0034] As in the case of FIGS. 2a and 2 b, the plurality of MEMS switchdevices 10-1-10-4 of FIGS. 3a, 3 b and 4 are arranged on substrate 12about a vertical axis A through the substrate, each switch 10 beingdisposed in a circular arrangement centered on axis A (central point 7)with each switch 10 being preferably spaced equidistantly along thecircumference of the imaginary circle B defining the circulararrangement. Thus, the MEMS switches 10 are preferably disposed in acircular arrangement around central point 7 on substrate 12. Note thatthe switches 10 lie on indicated by the circular line identified by theletter B. Note also that the switches are preferably arrangedequidistantly along the circumference of the circular line identified bythe letter B.

[0035] In FIGS. 2a and 3 a the DC control lines 11 and 22 are depictedas being thinner than are the RF lines 1-4. If the DC lines are muchthinner than the RF lines, they will have a higher impedance andcoupling with the RF lines will be thereby reduced. While the percentageby which the DC are made thinner than the RF lines is somewhat a matterof tradeoffs, it is believed their width should preferably be about 25%of the width of the RF lines or less. The DC lines should be separatedby at least one RF line width from the RF lines to reduce unwantedcoupling. The MEMS switches may be wired to their RF lines, DC controllines, ground pads or lines by means of wires 13 bonded to therespective switches 10 and their various lines and/or pads.

[0036] Yet another embodiment of this structure is shown in FIGS. 5a and5 b. In this embodiment, both the DC bias switch control lines 23, 24associated with each switch 10 are fed through vertical metal platedvias 21, 26. For each switch 10, one of the lines (line 24) is groundedby means of via 21 contacting ground plane 18 and the other line (line23) is connected, by means of a via 26 through a hole in the groundplane 18, to a trace 27 on the back side of the board 12 which functionsas a MEMS switch 10 control line. This reduces clutter (lines which donot directly assist the RF capabilities of the switch arrangement) onthe front of the board, and can allow for more complex switchingcircuits and for reduced coupling between the RF lines and the DC biaslines 11.

[0037] In the embodiment of FIGS. 5a and 5 b, all of the DC bias lines11 pass through metal plated vias 21, 26. Half of them contact theground plane 18 and the other half pass through the ground plane tocontact traces 27 on the back side 13 of the board 12.

[0038] Several geometries have been described which are based on acommon theme of a radial switching structure, with discrete RF MEMSdevices 10 assembled around a common input port 7 of microstrip line 14,and routing RF energy to one of several output ports (for example, ports1-4 in a four port embodiment).

[0039] It should be understood that the operation of the discloseddevice is reciprocal, in that the various ports described as the outputports could also serve as a plurality of alternate input ports which arefed to a common output port which is the central point 7. Furthermore,it should be understood that although 1×4 switching circuits have beenshown, other numbers of switches in the switching circuits are possiblesuch as 1×6 and 1×8 and possibly even higher numbers, and that thesedesigns will be apparent to one skilled in the art of RF design afterfully understanding the disclosure of this patent document. However, alarge number of ports may be difficult to realize due to crowding of theRF lines and he DG bias lines. This issue can be addressed by using themodification shown in FIGS. 6a and 6 b. In this embodiment, the RF andDC signals share lines 1, 2, 3, 4. Both the RF and the DC ports of theMEMS switches 10-1 . . . 10-4 are connected together, as shown in FIG.6a. The DC portion of the signal may be separated from the RF portion byusing an inductor 32-1 . . . 32-4 in each of the switches' DC circuit.This may be either a lumped element, a printed inductor, or an inductivestructure such as a very high-impedance RF line. Another inductor 34 maybe needed to separate the RF signal from the DC ground as shown in FIG.6b. In that case, the end of inductor 34 remote from the connection tovia 20 is coupled to a line 15 at ground potential. If it is necessaryto prevent the DC signal from reaching other RF components, then anexternal DC blocking capacitor may be used on each of the RF lines.These capacitors are not shown in the figures. FIGS. 6a and 6 b show afour port arrangement, but it is to be understood that this modificationwould be more apt to be used where space constraints do not allow theother embodiments to be easily utilized.

[0040] In another aspect of this invention, the radial switchingstructure described above is combined with a printed antenna structurewhich may or may not share the same substrate 12. In the embodiment ofFIG. 7, the printed antenna structure 40 preferably includes fourconductive cloverleaf elements 36 which define flared notch antennas 37therebetween. The DC bias lines 11 a disposed on the back side of theboard, as well as the common RF line 14, also on the backside of theboard, are shown in dashed lines. The selectable RF lines on the frontside of the board are shown in solid lines. The conductive cloverleafelements are preferably formed on one surface of board 12 usingconventional printed circuit board fabrication techniques. Thus, thecloverleaf elements 36 may be made by appropriately etching acopper-clad printed circuit board, for example. The lines on the bottomside (shown dashed) can be similarly made by appropriately etching acopper-clad printed circuit board.

[0041] Each flared notch 37 is fed by a separate microstrip line 1-4,each of which crosses over the notch of an antenna and is shorted to theground plane 18 (see, e.g., FIG. 5b) on the opposite side of board 12 atvias 39. These microstrip lines correspond to the similarly numberedports 1-4 discussed with respect to the switch arrangements of theearlier mentioned figures. RF energy passing down these microstrip linesis radiated from the associated antenna structure in a direction thatantenna is pointing (i.e. along the mid-points of the notch of the notchantenna which is excited). The DC bias lines 11 and 11 a are preferablyrouted to a common connector 41 on the bottom side of the board 12 andthe RF input preferably comprises a single feed point 42 which is routedto one of the four antenna structures (by means of one of themicrostrips 1-4) as determined by which MEMS switch 10 (see FIG. 5atheswitches 10 are too small to be shown clearly on FIG. 7, but they areclustered around point 7) is closed. Bias lines 11 are disposed on thetop side of board 12 while bias lines 11 a are disposed on the bottomside thereof. They are coupled together through the board 12 by means ofvias. A pad 8 of one via is numbered in FIG. 7 (the other vias areunnumbered due to the limited space available around them for referencenumerals, but the vias can, nevertheless, be easily seen). The vias inFIG. 7 are shown spaced further from the center point 7 than they wouldbe in an actual embodiment, merely for ease of illustration.

[0042] An embodiment more complicated than that of FIG. 7 is shown inFIG. 8. This embodiment has eight flared notches 37 defined bycloverleaf elements 36 and a single 1×8 array of RF MEMS switches 10 atthe central point 7 (see FIG. 5a—the switches 10 are again too small tobe shown easily on FIG. 8, but they are nevertheless clustered aroundcentral point 7). This antenna uses the 1×8 MEMS switch to route thecommon input port to one of eight flared notch antennas 37. This drawingonly shows the general concept of the structure and does not show therequired DC bias lines or inductors. But those bias lines would besimilar to those shown in FIG. 7, but more numerous given the fact thatthis embodiment has eight notches 37 rather than four notches 37.

[0043]FIGS. 7 and 8 demonstrate that the matrix of single-pole,multi-throw MEMS switches can be combined with an antenna structure 40to create a switched beam diversity antenna of rather inexpensivecomponents. The structure shown by FIG. 7 uses four flared notches 37,which are addressed by a 1×4 MEMS switch matrix preferably arranged inthe radial configuration described above.

[0044] The preferred embodiment of the hybrid single-pole, multi-throwswitch has been described with reference to FIGS. 3a and 3 b. It is feltthat this embodiment can be rather easily manufactured. The antennacloverleaf design of FIG. 8 is preferred since eight slots provide gooddiversity control. However, there may be other embodiments, and otherways of solving the problems associated with the candidate structuredescribed with reference to FIG. 1. One such solution is shown in FIG.9.

[0045] The embodiment of FIG. 9 is not a presently preferred embodimentof this invention, but it is an embodiment that may have sufficientadvantages in certain applications, such as when metal plated viascannot be used, that some practicing the present invention may choose toutilize it. This may be the case when a monolithic approach is taken,when vias and internal ground layers may not be feasible or may not besimple to realize. This embodiment builds on the concept that theindividual MEMS devices 10 are preferably clustered as closely aspossible around a central point 7 to avoid parasitic reactance. Thisembodiment also recognizes that this may not be possible for a design tohave a large number of ports, because when the microstrip transmissionlines are brought too close to each other, unwanted coupling occurs. Toaddress both of these problems, a 1×3 switching unit SU is used as abuilding block for a 1×N switch of any desired size. Each SU has a pairof MEMS switches 10 for coupling the transmission lines to a centralpoint 7 of the SU. Each transmission line port 1,2 of a first unit isaccessed through a MEMS device 10, while subsequent transmission lineports (for example, ports 3,4 of a second SU) are accessed through oneor more third MEMS device(s) 45 which route the RF signals alongsections of central transmission line 46 (which may now be of any lengthrequired to minimize coupling between ports) to a next 1×3 switchingunit SU. Each switching unit SU comprises two (or possibly more) MEMSswitches 10 clustered around its own central point 7 for coupling thetransmission lines thereto and another MEMS switch 45 for passing theincoming signal to yet another switching unit SU. In this and in eachsubsequent block SU, two additional (or more) transmission lines may beaddressed each through their own individual MEMS device 10, or thesignals may be sent to the next SU through the third MEMS device 45.Since unused sections of transmission line are switched off when theyare not used, they do not present unwanted parasitic reactance. Ofcourse, all of the DC bias methods described in previous embodiments maybe applied to this structure as well. Furthermore, other structures thatuse the 1×3 building block in this way, to allow necessary but unwantedsections of transmission lines to be turned off when not in use, will beapparent after this invention is understood. One example of anotherdesign would be a corporate switching structure, as opposed to thelinear one presented here. In a corporate structure one input feeds twooutputs, each of which in turn feed two more outputs, and those outputseach in turn feed two more outputs, until you have 2 n outputs at theend. When it is drawn, it looks like a corporate organization chart withmany layers of middle management (hence the name).

[0046]FIG. 9 thus depicts an alternate design that may be used if acentral metal-plated via 20 feature of the earlier embodiments is notfeasible. The design of FIG. 9 uses a 1×3 switch SU as a building blockfor a 1×N switch of any size. It benefits from the knowledge thatdangling sections of RF line will cause parasitic reactance when theyare not used. In each 1×3 unit SU, the third switch 45 is opened if oneof the ports on that unit is selected by means of closing its associatedMEMS switch 10. If neither switch 10 is selected, the third switch 45 isclosed, and the signal is routed to the next SU. By using this geometry,the sections of RF line between units can be as long as is needed tominimize coupling between the selectable ports, because those sectionsof RF line are switched off when not in use. Of course, thisbuilding-block approach can be used to make any geometry of 1×N switch.

[0047] The MEMS switches 10 are preferably disposed in a circulararrangement around central point 7. Note that in this embodiment theswitches 10, 45 also preferably lie on an imaginary circle, here againidentified by the letter B. Note also that the switches 10, 45 andsegment 46 are preferably arranged equidistant ly along thecircumference identified by the letter B.

[0048] In the numbering of the elements in this description and in thedrawings, numbers such as 10-2 appear. The first portion (the 10 in thiscase) refers to the element type (a MEMS switch in this case) and thesecond portion (the 2 in this case) refer to a particular one of thoseelements (a second MEMS switch 10 in this case). This numbering schemeis likely self-explanatory, but it is nevertheless here explained forthe reader who might not have previously encountered it.

[0049] The MEM switches 10-1 . . . 10-4 and 45 may be provided withintegral impedance matching elements, such as capacitors, in order toincrease the return loss to more than 20 dB. For that reason, the MEMswitches disclosed by US Provisional Patent Application Serial Number______ filed ______ and entitled “RF MEMS Switch with IntegratedImpedance Matching Structure” (attorney docket 620650-7) are believed tobe the preferred MEM switches for use in connection with this invention.

[0050] Having described the invention in connection with certainembodiments thereof, modification will now certainly suggest itself tothose skilled in the art. A such, the invention is not to be limited tothe disclosed embodiments except as required by the appended claims.

What is claimed is:
 1. A switch arrangement comprising: (a) a pluralityof MEMS switches arranged on a substrate about an axis through saidsubstrate, each MEMS switch being disposed on a common imaginary circlecentered on said axis, and each MEMS switch being spaced equidistantlyalong the circumference of said imaginary circle; (b) a conductive viain said substrate arranged parallel to and on said axis; and (c)connections for connecting a RF port of each one of said plurality ofMEMS switches with said conductive via.
 2. The switch arrangement ofclaim 1 wherein the substrate has a ground plane therein, saidconductive via passing through said ground plane without contacting saidground plane.
 3. The switch arrangement of claim 2 further including aplurality of strip lines, each one of said plurality of strip linesbeing coupled to a RF contact of one of said plurality of MEMS switches.4. The switch arrangement of claim 3 wherein said plurality of striplines are radially arranged relative to said axis.
 5. The switcharrangement of claim 4 wherein said plurality of strip lines and saidplurality of MEMS switches are disposed on a first major surface of saidsubstrate.
 6. The switch arrangement of claim 5 further including aplurality of control lines disposed on said first major surface of saidsubstrate, each control line being coupled to an associated one of saidplurality of MEMS switches and being disposed between two adjacent striplines.
 7. The switch arrangement of claim 6 wherein each of theplurality of control lines has a first width and wherein each of theplurality of strip lines has a second width, the second width being atleast three times greater than the first width.
 8. The switcharrangement of claim 6 further including a plurality of conductive viasin said substrate arranged parallel to said axis and contacting saidground plane, each of said plurality of MEMS switches having a DC groundcontact which is wired to one of the plurality of conductive viascontacting said ground plane.
 9. The switch arrangement of claim 8further including an impedance device coupling the conductive via on thecentral point to one of the plurality of conductive vias, the impedancedevice being disposed adjacent a second major surface of said substrate.10. The switch arrangement of claim 5 further including a plurality ofcontrol lines arranged in pairs and disposed on said first major surfaceof said substrate, each control line pair being coupled to an associatedone of said plurality of MEMS switches and being disposed between twoadjacent strip lines.
 11. The switch arrangement of claim 10 whereineach of the plurality of control lines has a first width and whereineach of the plurality of strip lines has a second width, the secondwidth being at least three times greater than the first width.
 12. Aswitch arrangement comprising a plurality of switch units, each switchunit having at least two MEMS switches coupled to a central point, theat least two MEMS switches of the switch unit being arranged to coupleselectively at least two transmission line ports to said central point,and at least a third MEMS switch coupled to said central point andadapted to be connected to a central point associated with an adjacentone of said plurality of switch units.
 13. The switch arrangement ofclaim 12 wherein each switch unit has a centrally disposed transmissionline, the centrally disposed transmission line connecting the switchunit to the at least a third MEMS switch associated with an adjacent oneof said plurality of switch units.
 14. The switch arrangement of claim13 wherein the centrally disposed transmission line is linearly arrangedfrom the central point of each switch unit towards the at least a thirdMEMS switch associated with an adjacent one of said plurality of switchunits.
 15. A switch arrangement comprising: (a) a plurality of MEMSswitches arranged on a substrate about a central point, each MEMS switchbeing disposed on a common imaginary circle centered on said centralpoint, and each MEMS switch being spaced equidistant ly along thecircumference of said imaginary circle; and (b) connections forconnecting a RF port of each one of said MEMS switches with said centralpoint.
 16. The switch arrangement of claim 15 wherein at least two ofthe MEMS switches are arranged to couple selectively at least twotransmission lines to said central point and wherein a pair of the atleast two transmission lines are disposed co-linearly of each other. 17.The switch arrangement of claim 16 wherein at least one of the MEMSswitches is arranged to couple selectively the central point of theswitch arrangement to a central point associated with another switcharrangement via a transmission line segment.
 18. The switch arrangementof claim 16 wherein the substrate has a ground plane therein and theswitch arrangement further includes a conductive via in said substratearranged parallel to and on a vertical axis which is normal to a majorsurface of substrate and which passes through said central point, theconductive via passing through said ground plane without contactingsame.
 19. The switch arrangement of claim 18 further including aplurality of strip lines, each one of said plurality of strip linesbeing coupled to a RF contact of one of said plurality of MEMS switches.20. The switch arrangement of claim 19 wherein said plurality of striplines are radially arranged relative to said central point.
 21. Theswitch arrangement of claim 20 wherein said plurality of strip lines andsaid plurality of MEMS switches are disposed on a first major surface ofsaid substrate.
 22. The switch arrangement of claim 21 further includinga plurality of control lines disposed on said first major surface ofsaid substrate, each control line being coupled to an associated one ofsaid plurality of MEMS switches and being disposed between two adjacentstrip lines of said plurality of strip lines.
 23. The switch arrangementof claim 22 further including a plurality of conductive vias in saidsubstrate arranged parallel to said axis and contacting said groundplane, each of said plurality of MEMS switches having a DC groundcontact which is wired to a one of a plurality of conductive viascontacting said ground plane.
 24. The switch arrangement of claim 23further including an impedance device coupling a conductive via on thecentral point to one of the plurality of conductive vias, the impedancedevice being disposed adjacent a second major surface of said substrate.25. The switch arrangement of claim 21 further including a plurality ofcontrol lines arranged in pairs and disposed on said first major surfaceof said substrate, each control line pair being coupled to an associatedone of said plurality of MEMS switches and being disposed between twoadjacent strip lines of said plurality of strip lines.
 26. An antennacomprising a plurality of end fire Vivaldi antennas arranged in acloverleaf configuration in combination with the switch arrangement ofclaim 15 for controlling which one or ones of said plurality of end fireVivaldi antennas is or are active.
 27. An antenna comprising a pluralityof end fire Vivaldi antennas arranged in a cloverleaf configuration incombination with the switch arrangement of claim 15 for controllingwhich one of said plurality of end fire Vivaldi antennas is active. 28.A method of making a switch arrangement comprising: (a) disposing aplurality of MEMS switches on a substrate in a circular pattern about apoint; (b) disposing a plurality of RF lines disposed in a radialpattern relative to said point on said substrate; and (c) connectingsaid plurality of RF strip lines to a common junction point at saidpoint on said substrate via said plurality of MEMS switches wherebyoperation of a one of said plurality of MEMS switches couples a one ofsaid plurality of RF strip lines to said common junction.
 29. The methodof claim 28 wherein at least two of the MEMS switches of said pluralityof MEMS switches are arranged to couple selectively at least two RFlines to said point and wherein a pair of the at least two RF lines aredisposed co-linearly of each other.
 30. The method of claim 29 whereinat least one of the MEMS switches of said plurality of MEMS switches isarranged to couple selectively the common junction point to anothercommon junction point associated with another switch arrangement madeaccording to the method of claim 28 via a transmission line segmentdisposed on said substrate.
 31. The method of claim 30 further includingproviding a ground plane in the substrate and providing a conductive viain said substrate arranged parallel to and on an axis through said pointand normal to a major surface of said substrate, the conductive viapassing through said ground plane without contacting same.
 32. Themethod of claim 31 further including disposing a plurality of striplines on said surface and coupling each one of said plurality of striplines to a RF contact of one of said plurality of MEMS switches.
 33. Themethod of claim 32 wherein said plurality of strip line and saidplurality of MEMS switches are disposed on the first major surface ofsaid substrate.
 34. The method of claim 33 further including disposing aplurality of control lines on the first major surface of said substrate,each control line being coupled to an associated one of said pluralityof MEMS switches and being disposed between two adjacent strip lines.35. The method of claim 34 further including providing a plurality ofconductive vias in said substrate arranged parallel to said axis andcontacting said ground plane, each of said plurality of MEMS switcheshaving a DC ground contact which is wired to a one of the plurality ofconductive vias contacting said ground plane.
 36. The method of claim 35further including coupling an impedance device between (i) theconductive via connected to the common junction point and (ii) at leastone of the plurality of conductive vias, the impedance device beingdisposed adjacent a second major surface of said substrate.
 37. Themethod of claim 33 further including disposing a plurality of controllines arranged in pairs on the first major surface of said substrate,each control line pair being coupled to an associated one of saidplurality of MEMS switches and being disposed between two adjacent striplines.
 38. A switch arrangement comprising: (a) a plurality of MEMSswitches arranged on a substrate about a common RF port, the RF porthaving a centerline and each MEMS switch being disposed spacedequidistantly from the centerline of said RF port; and (b) connectionsfor connecting a RF contact of each one of said MEMS switches with saidcommon RF port.
 39. The switch arrangement of claim 38 wherein thecenterline of the RF port is disposed perpendicular to a major surfaceof said substrate.
 40. The switch arrangement of claim 38 wherein thecenterline of the RF port is disposed parallel to a major surface ofsaid substrate.